Ultrasound Measurements of the Median Nerve at the Distal Wrist Crease Correlate With Electrodiagnostic Studies

Abstract

Background: Carpal tunnel syndrome (CTS) is the most common nerve entrapment neuropathy and is commonly evaluated using electrodiagnostic studies (EDSs). Ultrasound (US) has emerged as a potentially easier and more comfortable alternative to EDSs. The purpose of this study is to evaluate whether measurements of the cross-sectional area (CSA) of the median nerve via US correlate with the severity rating of CTS based on EDSs. Methods: A retrospective review of patients aged 18 years or older who underwent US and EDSs of the median nerve for CTS was performed. Sensory nerve action potential, distal motor latency, and compound muscle action potential were measured, and severity was graded on American Association of Neuromuscular and Electrodiagnostic Medicine guidelines. Cross-sectional area of the median nerve was measured via US at the wrist crease. Results: There was a significant association between increasing CSA and increasing EDS severity (P < .0001). The mean CSA for normal, mild, moderate, and severe CTS was 7.48 ± 2.00, 10.36 ± 2.53, 12.01 ± 3.64, and 14.34 ± 4.77 mm², respectively. The area under the curve demonstrated the ability of median nerve CSA to discriminate between normal and abnormal EDSs with an optimal cutoff CSA of ≥10 mm², as well as, the ability to discriminate between mild CTS and moderate to severe CTS at a cutoff CSA of greater than or equal to 12 mm². Conclusions: The results of this study show that US measurements of the median nerve at the distal wrist crease discriminate between normal and abnormal EDSs, and between mild CTS and moderate to severe CTS.